This invention relates to a spacer forming method and a spacer forming apparatus for maintaining a constant gap to be filled with liquid crystal between opposite substrates to be used for a liquid crystal panel, and more particularly to a spacer forming method and a spacer forming apparatus for dropping ink dispersing spacers in solvent onto spacer forming positions by an ink jet method (or drop discharging method).
Response, contrast and view angle required for a liquid crystal panel depend considerably on the thickness of the liquid crystal layer. Accordingly, the thickness thereof is so controlled to be constant by interposing spacers between the opposite substrates. In the known spacer forming method, the spacer is formed pillar-like on the substrate or ball-like spacers are scattered on the substrate.
A photolithography process or etching process is required for forming the pillar-like spacers. The number of steps is large. The cost is high and the manual labor is considerable. A spraying method (Wet type) and a granular spacer dispersing method (Dry type) are used for forming the ball-like spacer with pressurized nitrogen gas. In both of the methods, spacers are dispersed also on the region of the pixels that causes lowering of the brightness and irregularity of the latter. The spacer distribution is nonuniform and the gap between the opposite substrates is sometimes nonuniform.
In the patent literature 1, such a technique is disclosed wherein ink is simply jetted onto a black matrix as a non-pixel region. In this method, ink with granular spacers dispersed in solvent is dropped onto the black matrix from a nozzle. The solvent is evaporated and the spacers remain on the black matrix.
When the nozzle is clogged or a nozzle plate having nozzle openings is damaged thereby causing discharging trouble, spacers are not formed on the corresponding positions or the spacer forming positions are disordered. The thickness of the liquid crystal layer becomes uneven. The display quality is deteriorated. For example, when the nozzles of No. 8 and No. 17 as shown in FIG. 17 are defective in rows, spacer defects occur in the rows as shown by white circles.
The patent literature 2 discloses the a method of preventing a spacer forming defect due to abnormal spacer jetting. In that method, the ink jetted from the nozzle is observed with a camera or picture processing apparatus to measure the jetting speed of the ink and the jetting direction of the ink. When the measuring results are out of the predetermined range, the nozzle is judged to be abnormal and the nozzle is cleaned.
Patent Document 1: JP7-118835A
Patent Document 2: JP2000-17440A